Stress relieved welded steel composite

ABSTRACT

A LOW ALLOY HIGH STRENGTH STEEL WELD DEPOSIT OF HIGH TOUGHNESS AND SUPERIOR RESISTANCE TO THERMAL DEGRADATION AND WHICH, AFTER A STRESS RELIEF CONSISTING OF A 16-HOUR SOAK AT 1025*F. FOLLOWED BY COOLING AT A RATE OF 200*F. PER HOUR, HAS CHARPY V-NOTCH IMPACT STRENGTH OF AT LEAST 20. FT.-LBS AT-60*F. AT YIELD STRENGTH LEVELS WHICH ARE SELECTABLE BETWEEN ABOUT 90K S.I. AND ABOUT 145K S.I, THE DEPOSIT CONSISTING ESSENTIALLY OF   PERCENT BYWEIGHT   ELEMENT BOARD PREFERRED   CARBON 1.12 1.10 MANGANESE 25-.9 35-.75 SILICON .20-.70 .25-.55 CHROMIUM .2-2.0 .2-1.35 NICKEL 2.0-4.5 3.0-4.0 MOLYBDENUM .2-1.2 .35-1.0 PHOSPHORUS 1.020 1.012 SULFUR 1.020 1.012 IRON BALANCE BALANCE   1MAXIMUM.   ALSO A LOW ALLOY STEEL WELD DEPOSIT HVING A YIELD STRENGTH OF A LEAST 130K S.I. AND CHARPY V-NOTC ENERGY ABSORPTION AT-60*F. OF A LEAST 20 FT.-LBS. AFTER BEING STRESS RELIEVED BY SOAKING FOR 16 HOURS AT 1025*F. FOLLOWED BY COOLING AT A RATE OF 200*F. PER HOUR, THE DEPOSIT CONSISTING ESSENTIALLY OF   PERCENT BY WEIGHT   SPECIFIC ELEMENT BOARD PREFERRED EXAMPLE   CARBON .05-.12 .07-.10 .08 MANGANESE .25-9 .35-.75 .5 SILICON .20-.70 .25-.55 .4 CHROMIUM .6-2.0 .75-1.35 1.0 NICKEL 2.0-4.5 3.0-4.0 3.5 MOLYBDENUM .3-1.2 .5-1.0 .75 PHOSPHORUS 1.020 1.012 &lt;.01 SULFUR 1.020 1.012 &lt;.01 IRON BALANCE BALANCE BALANCE   1MAXIMUM.

United States Patent 3,667,924 STRESS RELIEVED WELDED STEEL COMPOSITEWilliam T. De Long and Paul T. Corcoran, West Manchester Township, YorkCounty, Pa., assignors to Teledyne Inc., Los Angeles, Calif. No Drawing.Filed Dec. 30, 1969, Ser. No. 889,320 Int. Cl. B23b 15/00; B23p 3/00 US.Cl. 29-1961 1 Claim ABSTRACT OF THE DISCLOSURE Percent by Weight ElementBroad Preferred Carhom 12 10 Manganese 25-. 9 35-. 75

lllcon 20-. 70 25-. 55 Chromium-.. .2-2. 0 2-1. 35 Ni kel 2. 0-4.5 3.0-4.0 Molybden 2-1. 2 35-1. 0 Phosphorus. O20 O12 Suli 020 l 012 IronBalance 1 Maximum.

also a low alloy steel weld deposit having a yield strength of at least130K s.i. and Charpy V-notch energy absorption at 60 F. of at least 20ft.-lbs. after being stress relieved by soaking for 16 hours at 1025 F.followed by cooling at a rate of 200 F. per hour, the deposit consistingessentially of Percent by Weight Specific Element Broad Preferredexample Carbon 05-. 12 07-. 08 25-. 9 35-. 75 5 20-. 70 25-. 55 4 6-2. 075-1. 35 l. 0 2. 0-4. 5 3. 0-4. 0 3. 5 .31.2 .5-1.0 .75 020 012 01 020012 01 Balance Balance Balance 1 Maximum.

The invention herein described was made in the course of or under acontract or subcontract thereunder with the Department of the Navy.

This invention relates to steel weld deposits; more particularly itrelates to low alloy high strength steel weld deposits characterized byimproved toughness and superior resistance to thermal degradation duringstress relief.

In the field of low alloy high strength steels with yield strengthsabove 90K s.i., particularly HY-l30/ 150 type steels (covered byMilitary Specification MIL-S-2437l (SHIPS), dated Dec. 19, 1968) withyield strengths of at least 13K s.i., there has been a need for highperformance weld metals which in a single deposit will have yield andtensile strengths and impact toughness approximately equal to those ofthe base metal in both the as-deposited and the stress-relievedconditions. Weld deposited metal is always under a handicap comparedwith plate material and must be more shrewdly formulated because itlacks the advantages of the mechanical hot work treatments which producegrain refinement in plate material. In spite of this handicap low alloysteel weld deposit analyses and methods of deposition have beendeveloped which produce as-deposited metal with yield strength at leastmatching that of the available hot worked and heat treated platematerial, coupled with suitable toughness. Requiring the highest qualitywelding processes, such deposits were recently produced by means ofinert gas shielded methods used with high purity alloy-bearing fillerwires. This level of performance has first been achieved with depositsfrom manual low hydrogen lime-fluoride covered electrodes, which was amore diflicult goal. However, all such weld metals, by whatever processthey have been produced, have heretofore been susceptible to temperembrittlement produced during thermal stress relief treatments, whichlowered their impact strength below the desired level of 20 ft.-lbs. at60 F.

We are able to produce weld deposits which when applied according torecommended principles known to the art and described hereinafterexhibit yield strengths selectable between K s.i. and about 145K s.i.and Charpy V-notch impact energy absorption of over 20 ft.- lbs. at 60F. both in the as-deposited condition and after a standard stress relieftreatment consisting of a 16- hour soak at 1025 F. followed by coolingat a rate of 200 F. per hour. Other mechanical properties of our newweld deposits, such as percent elongation, tensile strength, reductionof area, hardness and yield strength-to-tensile strength ratio remainsatisfactory after such stress relief.

Our new weld deposits were developed in connection with a study of theHY-/ 150 area, which currently requires a 130K s.i. minimum yieldstrength, although they have been found broadly to have yield strengthswhich are selectable between about 90K s.i. and about K s.i. As comparedto earlier weld metals of the HY 130/150 type, which are suitable foras-welded use but not for stress relieved use, our weld deposits arecharacterized by a novel balance of those chemical elements which haveproven most effective in the as-welded grades, and also by a retentionof the earlier emphasis on limitations in the harmful elementsphosphorus and sulfur to levels below .020 percent by weight andpreferably below .012 percent by Weight.

A particularly attractive aspect of our weld deposits is that they mayexhibit desirable stress-relieved properties when deposited with lowhydrogen lime-fluoride covered electrodes utilizing conventionalcommercial quality rimmed steel core wires. Such electrodes, which werethe chosen means for producing weld deposits which established theexistence and limitations of our invention, ofler significant economicadvantages over the simpler but much more expensive high purity wire andgas-metal-arc (GMA) processes which are also applicable and which haveheretofore been widely used in investigating and producing HY-l30/ weldmetals.

Accordingly, we provide a low alloy high strength steel weld deposit ofhigh toughness and superior resistance to thermal degradation and which,after a stress relief consisting of a 16-hour soak at 1025 F. followedby cooling at a rate of 200 F. per hour, has Charpy V-notch impactstrength of at least 20 ft.-lbs. at 60 F. at yield strength levels whichare selectable between about 90K s.i. and about 145K s.i., the depositconsisting essentially of In a preferred form the deposit consistsessentially of Percent by weight Carbon max .10 Manganese .35.75 Silicon.25.55 Chromium .21.35

Nickel 3.0-4.0 Molybdenum .35-l.0 Phosphorus max .012 Sulfur max .012

Iron Balance In embodiments especially suited for use in weldingHY-130/150 base material we provide a low alloy steel weld deposithaving a yield strength of at least 130K s.i. and Charp'y' V-notchenergy absorption at -60 F. of at least 20 ft.-lbs. after being stressrelieved by soaking for 16 hours at 1025 F. followed by cooling at arate of 200 F. per hour, the deposit consisting essentially of Percentby weight Specific Element Broad Preferred example Carbon 05-. 12 07-.10 08 Manganese 25-. 9 35-. 75 5 Silicon 20-. 70 25-. 55 4 Ghrom1um 6-2.75-1. 35 l. 0 Nickel 2. 0-4. 3. 0-4. 0 3. 5 Molybdenum 3-1. 2 6-1. 0 75Phosphorus 020 012 01 Sulfur 020 012 01 Iron Balance Balance Balance 1Maximum.

Realization of the optimum properties of our new weld deposits willdepend on the conditions under which they are deposited, as will beappreciated by those skilled in the art. In the HY- 130/150 area certainpractices, such as low welding heat input and small head size, are knownto maximize as-welded strength and toughness of the deposit. In additionto such general practices the specific welding process employed toproduce our new weld deposits will have a definite effect on the degreeof retention of the maximum deposit properties attainable; it is wellestablished that the higher the Weld metal purity, the more itsproperties will approach the optimum for its overall alloy balance.Purity in this context not only means low levels of residual or trampelements such as phosphorus, sulfur, nitrogen and oxygen but alsoincludes aspects such as size and shape of inclusions, etc. Thegastungsten-arc (GTA) process with pro-alloyed high purity filler metaladditions, which provides the highest purity weld metal, can be expectedto be optimum for producing our deposits; somewhat lower on the scale,although still very good, is the GMA process utilizing argon-oxygen orequivalent shielding gases and pre-alloyed electrode wire. As aboveindicated, we have also found that our new analysis can be welddeposited with good. results close to those obtained with the GMAprocess and at much lower cost with properly formulated high quality lowhydrogen lime-fluoride covered electrodes. Deposits produced by othertypes of covered electrodes or submerged arc welding can be expected toexhibit inferior properties to a degree dependent on the specificprocess used and the purity of the resultant weld metal.

The low hydrogen lime-fluoride covered electrode which we have used forproducing our deposits meets a general specification for this class ofelectrode, and consists of a mild steel core and a lime-fluoride coatingthereon, the electrode containing by weight about 45 percent to aboutpercent core and about 20 percent to about 55 percent coating, thecoating containing by weight of the electrode up to about 30 percentiron powder and alloying metal powder, about 2 percent to about 7percent deoxidizer metal powder, about 4 percent to about 15 percentmetal fluoride, about 5 percent to about 15 percent alkaline earthcarbonate, 0 to about 10 percent slag builder and modifier and about .5percent to about 8 percent inorganic binder material. Although we havechosen to supply all alloy by way of the coating for reasons of economyin our electrode, it is of course possible to introduce all or part ofthe alloy through the core wire.

Other details, objects and advantages of the invention will becomeapparent as the following description of certain present preferredembodiments thereof proceeds.

TABLE 1 Welding procedures-HY-/ test series Plate material: 2 pieces ofone inch thick U.S. Steel HY- 130(T) plate minimum dimensions 10" long x4" wide.

Chemistry-0.12% C, 0.90% Mn, 0.34% Si, 0.59% Cr, 4.96% Ni, 0.50% Mo,0.002% P, 0.008% S, 0.06% Cu, 0.064% V, 0.025% A1.

Joint: Type-single V PreparationFlame cutting followed by grindingBevel-422V: on plate Electrode: Diameter% Coating'l..oot hydrogenlime-fluoride type.

Core wire: Type-conventional commercial-quality rimmed steelChemistry-0.07% C, 0.50% Mn, 0.005% Si,

0.007% P, 0.020% S. Backup plate: U.S. Steel HY-130(T) one-inch-thiclrplate, one inch minimum in width x joint length Welding position: FlatWelding current: :5 amps DC, reverse polarity Welding voltage: 24 voltsHeat input: 30:2 kilojoules per inch Preheat and interpass temperature:250 F.:25 F. Interpass delay: 1 hour minimum.

Table 1 lists constant parameters maintained throughout a test seriesrun with diameter low hydrogen lime-fluoride covered electrodes tocompare the performance of our Weld deposits with other weld deposits ofessentially the same as-Welded strength. This series was designedprimarily to explore the general HY-l30/ 150 area. In order to minimizethe eifects of welding process variables on the performance of thedeposits, a major eflort was made to keep the welding of all test platesidentical within the limitations inherent in shielded metal arc welding.Only one welder and one power source were used throughout the series.All test weldments were made in the Hat position using reverse polaritydirect current. Multipass Welds were preparing using stringer beads anda temper bead deposition sequence. Welding parameters were controlled sothat a calculated heat input of 30:2 kilojoules per inch would bemaintained. Each pass in the test weldment was completed with oneelectrode only and no starts or stops were located in the test area.Preheat and interpass temperatures of the test weldment were maintainedat 250:25 F. In an attempt to preclude any hydrogen-caused cracks in thedeposit a. one hour minimum interpass delay time was used. All Weldmetaltensile bolts (.357" diameter) and Charpy V-notch impact specimens weremachined from the deposits and tested both in the as-welded conditionand after a 16-hour soak at 1025 F. followed by cooling at a rate of 200F. per hour.

TABLE 2 [Weld deposit chemical analysis] Deposit Mn Si Cr N1 M0 P B A.077 1.07 .41 1.09 3.52 .35 .003 .004 B--. .086 .76 .44 .78 5.14 .18.002 .004 o.-. .122 .55 .47 .53 6.26 .35 .002 .004 D--- .076 1.09 .38.50 3.56 .74 .003 .005 E.-- .084 .84 .45 .73 5.10 .55 .004 .003 F .083.56 .36 .98 3.62 .75 .004 .002 G .126 1.07 .41 .52 3.60 .39 N/D N/D H---.133 .59 .53 .54 3.65 .75 N/D N/D 1-- .086 .77 .47 .80 5.14 .57 I N/D BN/D J .124 .53 .45 .96 3.68 .36 N/D N D K- .084 .79 .45 1.25 5.08 .58 IN/D N/D L. .032 .32 .42 .76 5.17 .55 N/D I N/D M .088 .66 .53 .52 3.53.39 N/D N/D N- .101 1.16 .40 2.60 .25 .90 'N/D N/D 0- .079 .73 .371.51 1. 90 .73 I NIB 1 N/D P 1 .084 .83 .43 .76 2.22 .55 NIB 1 N/D Q..48 .32 .98 1.97 1.23 NIB 1 N/D R .48 .27 .96 3. .78 1 N/D 1 N/D 1Examples of applicants improved weld deposits.

I N/D: Not determined-estimated at less than .010 percent; in same rangeas Deposits A through F.

With the above described constant preparation and 0 testing conditions,the weld deposits had the chemical analyses listed in Table 2. Theexperiments employed were selected to fall into compositional arrays orpatterns which were most favorable to graphical and statistical studiesof the physical effect conferred by each alloying 25 element.

elements, their compositions were selected to reveal alloy effects withthe minimum number of tests. Deposits F, J and R meet the requirementsfor HY-130/ 150 type weld metals, showing yield strengths greater than13 UK s.i. both as-Welded and after stress relief; deposits M and -P aresomewhat lower than 130K s.i. in yield strength but still show excellentoverall properties both as-welded and after stress relief.

Graphical and statistical study of the data generated in this and otherseries produced the above described limits on analyses of deposits ofthe invention.

We are unable to state with certainty why the alloy balance of ourimproved weld deposits is superior to that of similar known low alloyhigh strength weld deposits in the retention of properties on stressrelief, particularly toughness at F.; however, it appears that the chieffactor is low manganese, combined with increased chromium wherenecessary to maintain the strength level. For example, deposit D inTables 2, 3 and 4 is a typical known deposit with very good as-weldedproperties (Table 3); stress relief of this deposit causes severeembrittlement, as indicated by the drastic deterioration in CharpyV-notch toughness at all three testing temperatures (Table 4). Deposit Dcontains 1.09 percent manganese and .50 percent chromium; deposit F, apreferred embodiment of our improved weld deposits for use in TABLE 3[As-welded weld deposit mechanical properties] Yield strength Elonga-Reduc- Charpy V-notch energy absorp- (0.2% Tensile Yield] tion in tion01 tion, it.-1b. Deposit oflset) strength, tensile 1.4 in., area, NumberK s.i K s.i. ratio percent percent F. F. -60 F.

Not tested in as-welded condition 123 140. 5 88 19. 3 66. 7 107. 5 78 39Not tested in as-welded condition 1 Examples of applicants improved welddeposits.

TABLE 4 [Stress-relieved weld deposit mechanical properties] Yieldstrength Elonga- Reduc- Charpy V-notch energy absorp- (0.2% TensileYieid/ tion in tion 01 tion, it.-lb. Deposit ofiset) strength, tensile1.4 in. area, Number K s.i. K s.i ratio percent percent +80 F. -0 F. -60F.

132 139 95 17. 9 60. 7 35 18. 5 13. 5 136 141 96 17. 2 55. 5 24 12. 510. 5 146 159. 5 92 19. 3 55. 5 28. 5 18. 5 9. 5 146 153. 5 95 19. 3 59.9 10 8. 5 4 141 152 93 17. 2 47. 0 11 9 8 142 153 93 18. 6 60. 7 69. 546. 5 27. 5 142 150. 5 94 18. 6 54. 8 32. 5 l8. 5 13 158 168 94 16. 445. 4 20. 5 12 6. 5 158. 5 91 19.3 55.5 7 5. 5 3. 5 137. 5 148. 5 93 14.3 56. 3 51. 5 32 20. 5 136. 5 151 90 17. 2 61. 3 11 10 8. 5 142 153 9316. 4 59. 9 l3 8 5. 5 123 132. 5 93 20. 0 61. 3 115. 5 106. 5 65 140 15491 20. 0 59. 9 43. 5 2A 14. 5 130 142 92 21. 5 62. 7 68 41 15 128 141 9120. 0 64. 1 96. 5 87. 5 46 136 149 91 18. 6 59. 9 43. 5 18.5 12 134 14692 20. 0 58. 5 65. 5 46. 5 22 1 16-hour soak at 1,025 F., followed bycooling at 200 F. per hour. 3 Examples of applicants improved welddeposits.

Results of mechanical tests in the as-welded condition are listed inTable 3 and those of tests in the stress-relieved condition are listedin Table 4.

As indicated in the tables, weld deposits F, J, M, P and R are examplesof our improved weld deposits. While the other deposits shown areoutside the compositional limits of our improved weld deposits inrespect to one or more the HY-130/ area, is virtually identical todeposit D except that it contains .56 percent manganese and .98 percentchromium, just the reverse of the quantities of those elements indeposit D. The lower limit of .25 percent on manganese is effective inavoiding possible problems due to insufiicient tying up of sulfur withmanganese below this level. While nickel has always been a principalalloy element relied upon to improve low temperature impact strength,our investigation shows that nickel has a somewhat unclear eifect; ourevidence indicates that levels of about 2 percent and about 3.5 percentare both favorable to good stress-relieved toughness, with 3.5 percentnickel being optimum, but we have found that high nickel, on the orderof 5 percent or higher, is definitely harmful to stress-relieved impactproperties. The low sulfur and phosphorus levels of our deposits, whilenot of themselves conferring high strength or good impact qualifies,certainly aid in maintaining good properties; all six deposits for whichphosphorus and sulfur were determined in the series of Tables 2 through4 showed very low phosphorus and sulfur levels but only deposit Fexhibited the desired stress-relieved mechanical properties. Limits onother elements in our deposits define what we believe to be the bestarea for securing the desired strength levels.

As above indicated, realization of maximum properties in our deposits isdependent on the use of favorable welding practices and parameters. Withunfavorable practices, such as high heat input, no interpass delay,etc., both the stress-relieved and the as-welded properties can beimpaired; however, even in such cases the stress-relieved properties,particularly toughness, of our improved Weld deposits can be expected tobe superior to those of similar known deposits subjected to the samepractices While we have described certain present preferred embodimentsof the invention it is to be distinctly understood that the invention isnot limited thereto but may be otherwise variously embodied within thescope of the following claims.

We claim:

1. A stress relieved composite which has been subjected to soaking for16 hours at 1025 F. followed by cooling 8 at a rate of 200 per hourcomprising a base consist ing essentially of Percent by weight havingthereon a weld deposit consisting essentially of Percent by weightCarbon .05-.l2 Manganese .25-.9 Silicon .20'.7 0 Chromium .6-2J0 Nickel2.0-4.5 Molybdenum .3-1.2 Phosphorus max .020 Sulfur max .020

Iron Balance References Cited UNITED STATES PATENTS 2,327,490 8/1943Bagasar l28 W 2,624,687 1/ 19'53 McMullan 75--128 W 3,175,902 3/1965Ferree 75-l28 W 3,254,991 6/ 1966 Shimmin 75-128 W 3,290,128 12/ 1966Manganello 75l28 T HYLAND BIZOT, Primary Examiner US. Cl. X.R. 148-34UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 316679924Dated June 6. 1972 (s) William T. DeLong and Paul T. Corcoran It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

At each of the following listed places in the specification, correct "K8.1." to read -ksi-:

Column 1, line 19 (2 occurrences) H H H H 26 (2 occurrences) I! H I H I!l H 2 H table 3, in the second and third column headings 4, in thesecond and third column headings Column 4, line 61, change "preparing"to -prepare--.

Column 5, in each of tables 2, 3 and 4, delete the brackets before andafter the table heading.

Signed and sealed this 26th day of September 1972.

Attest{ EDWARD M.FLETCHER,J R. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents ORM PC1-1050 (10-69) USCOMM-DC 60376-1 69 h u 5.GOVERNMENT PRINTING OFFICE: I969 0-366334

20. FT.-LBS AT-60*F. AT YIELD STRENGTH LEVELS WHICH ARE SELECTABLEBETWEEN ABOUT 90K S.I. AND ABOUT 145K S.I, THE DEPOSIT CONSISTINGESSENTIALLY OF